Heretofore, a medical needle such as an injection needle has included a metal needle, a hub provided on a proximal end of the metal needle for fixing the metal needle, and a cap capable of fitting on the hub and covering a tip of the metal needle to prevent accidental piercing. The injection needle is used with the cap covering the tip of the injection needle being detached. Then, after use, the tip of the injection needle contaminated with a patient's blood or body fluid is covered with the cap to prevent an operator, a patient, a person who discards the needle or the like from being injured by accidental contact with the sharp tip and from acquiring diseases such as hepatitis or various other kinds of infectious diseases.
Conventional injection needle assemblies capable of protecting a used injection needle safely and easily include such assemblies that a cylindrical shield provided so as to cover an outer cylinder of a syringe is slid toward a distal end of an injection needle to protect the injection needle (Japanese Patent Application Laid-Open Nos. 342200/1999, 319090/1999, 127765/1998, etc.); a shield hinged at a hub provided on a proximal end of an injection needle is rotated relative to the injection needle to protect the injection needle (Japanese Patent Application Laid-Open Nos. 57005/1999, 248930/1998 and 113392/1998); and a distal end of an injection needle is protected by a shield movable along the injection needle in the axial direction of the injection needle (Japanese Patent Application Laid-Open Nos. 206204/1996, 250898/1995, 148176/1995, etc.).
Such conventional injection needle assemblies require use of both hands of an operator for operation. The operation is that the operator has to hold a medical instrument using one hand and move the shield to protect the injection needle using the other hand. Further, since any of the injection needle assemblies is large in size, the injection needle assemblies generate an extremely large amount of waste.
On the other hand, one hand-operable injection needle assemblies have been developed in view of the problems described above (Japanese Patent Application Laid-Open No. 234264/1991, Japanese Utility Model Application Laid-Open No. 63050/1994 and Japanese Patent Nos. 2739840 and 2974299). In the one hand-operable injection needle assemblies, a needle guard capable of protecting at least the distal end of the injection needle is provided parallel to the axial direction of the injection needle and the proximal end of the needle guard extends as far as the injection cylinder. After use of the injection needle assemblies, the proximal end of the needle guard is pushed by any of the fingers of a syringe-holding hand to move the needle guard toward the distal end of the injection needle and the distal end of the injection needle is protected. Since such injection needle assemblies do not require both hands for operation, the operator can easily protect the injection needle.
However, in the one hand-operable injection needle assemblies described above, it is necessary, in order to provide the needle guard, to form an additional hole for insertion of the needle guard. The hole is formed by forming another hole, in addition to a hole for inserting an injection needle, in a needle hub or providing a separate member having a hole on the needle hub in the injection needle assemblies. In that case, it is difficult to assemble the needle guard with the needle hub.
Further, in the injection needle assemblies having a needle guard made of a hard resin (Japanese Utility Model Application Laid-Open No. 63050/1994, Japanese Patent Nos. 2739840 and 2974299), the needle guard is not adjacent to the injection needle but is positioned parallel to the injection needle and spaced apart from the injection needle, so that the size of such assemblies is large and the assemblies are difficult to use. Besides, in the injection needle assemblies described above, since the needle guard is provided on the assemblies at the distal side of the needle hub, the total length of the needle is made longer and it is difficult to pierce the needle into a patient.
Further, an injection needle assembly having a needle guard made of a flexible resin (Japanese Patent Application Laid-Open No. 234264/1991) has a mechanism in which a notch is formed along the axial direction of the needle guard and the injection needle is accommodated in the needle guard through the notch of the needle guard when the needle guard is slid along the injection needle to the distal end. However, it is necessary to form the notch in the needle guard to provide the mechanism described above, and the process for producing the mechanism requires a complicated step. In addition, the needle guard has to be considerably flexible and it is difficult to push the proximal end position of the needle guard to slide the needle guard on the injection needle using one hand when protecting the injection needle.
In view of the foregoing situations, an object of this invention is to provide a needle assembly which is compact in shape and easy to assemble, and can be operated using one hand.